The goal of this research project is to define the multiple mechanisms responsible for the distribution of myocardial blood flow in both dogs and pigs. Animals with normal size hearts and with left ventricular hypertrophy secondary to either a volume or a pressure overload will be studied. Methodology employed to measure transmural myocardial blood flow is 7-10 radioactive microspheres. The majority of the studies undertaken are carried out in the awake state. These studies include: 1) myocardial blood flow distribution with transient ischemia during infusions of nitroglycerin, propranolol, dopamine, and adenosine, 2) myocardial mechanics and wall stress-strain relationships in the control and hypertrophied hearts, 3) factors controlling blood flow in both pigs and dogs with chronic collateral vasculature, 4) collaborative studies of mitochondrial function in animals with stable left ventricular hypertrophy, and 5) high energyphosphate metabolism during transient ischemia.